Although applicable to any semiconductor chip systems, the present invention and the problem on which it is based is explained in relation to a micromechanical semiconductor chip system.
Customarily, semiconductor chips are manufactured as a composite on semiconductor wafers. Depending on the chip and wafer size, such semiconductor wafers contain up to several thousand components. After the semiconductor chips are produced in a composite on the semiconductor wafers, they must be separated from one another by dicing. This is normally carried out using a wafer saw.
A wafer saw has a circular saw blade having a width less than 100 μm, which rotates, for example at a rotational speed of 12000 rpm. The surface of the saw blade is coated with diamond chips. In order to cool the wafer surface and the saw blade during the sawing process as well as to clean off the particles produced during the sawing process, the surface of the wafer is rinsed with water.
This method is suitable for dicing semiconductor chips, which are insensitive to the action of particles and water at the end of the manufacturing process. However, many micromechanical sensor chips have structures which may be destroyed by the action of particles and/or water during the sawing process. A customary method for protecting such sensitive structures is to bond a cap onto the sensor chips before the semiconductor chips are diced.
An example of such micromechanical sensor chips is inertial sensors, which are used to measure measured quantities, which require no measuring medium for propagation or are able to pass through the cap, such as, for example, an acceleration sensor working on a capacitive measuring principle. A customary embodiment of the sensor chip has a very delicate finger structure, which would become stuck under the action of water. Since the sensor chip retains its function even when hermetically sealed, a cap is bonded to the substrate wafer before sawing.
An example of such a micromechanical structure, which is not to be hermetically sealed, is a micro total analysis system (μTAS). In such a system, units are integrated on a micro-fluidic chip for the preparation, separation and detection of chemical or biological solutions. The fluidic channels must have accesses in order to be able to infuse the analysate. The particles arising during the sawing process may accumulate in the accesses and clog them. Water could enter the system by capillary force and destroy the functionality of the μTAS.